ASA 127th Meeting M.I.T. 1994 June 6-10

4pSAb9. A general formulation for shaping PVDF film as volume velocity sensor for beams.

Francois Charette

Alain Berry

Catherine Guigou

G.A.U.S., Mech. Eng. Dept., Univ. de Sherbrooke, Sherbrooke, PQ J1K 2R1, Canada

Active structural acoustic control (ASAC) uses transducers placed directly on the vibrating structures. Normally, a relatively high number of sensors are needed for this type of active control. Recently, a new strategy using a single information of error, the volume velocity of the structure, was presented [Johnson and Elliott, Proc. Inst. Acoust., 411--420 (1993); Guigou and Berry, J. Acoust. Soc. Am. 93, 2351(A) (1993)]. It is possible to design a single sensor that gives the total volume velocity of a beam by using shaped PVDF film. Presently, there is two different approaches available for shaping PVDF film; (i) the quadratic approach developed by Johnson and Elliott, (ii) the modal approach used by Guigou and Berry. Both methods yield a volume velocity sensor that has the same length of the beam. Unfortunately, such a long sensor may be affected by the presence of other actuator that are along the beam. It is the case when an asymmetric actuation is used. The volume velocity sensor obtained by the formulation presented here can be of arbitrary length and positioned anywhere along the beam. Theoretical results are presented for different boundary conditions and compared to experimental results. The result shows, the shorter the PVDF film, the more it becomes sensitive to parameters such as; positioning, deformation due to higher modes, errors on the shape, etc.